Control systems for mining equipment

ABSTRACT

THE SPECIFICATION DESCRIBES A HYDRAULIC-PNEUMATIC ANALOG TRANSDUCER FOR PROVIDING A PNEUMATIC PRESSURE INDICATION OF THE HYDRAULIC PRESSURE EXISTING IN A HYDRAULIC RAM. THE TRANSDUCER MAKES USE OF A MEMBRANE OF WHICH ONE SIDE IS SUBJECTED TO THE HYDAULIC PRESSURE WHILE THE OTHER SIDE, IN ACCORDANCE WITH THE HYDRAULIC PRESSURE OBTAINING, VARIES IN ITS DISTANCE FROM THE END OF A TUBE. AIR IS CAUSED TO PASS BETWEEN THE RESULTING ANNULAR GAP BETWEEN THE END OF THE TUBE AND THE MEMBRANE AND THE RESULTING PRESSURE GRADIENT IS MEASURED BY MEANS OF A PENUMATIC PRESSURE GAUGE.

Feb. 16, 1971 "H. RIESCHEL v 3,563,094

CONTROL SYSTEMS FOR MINING EQUIPMENT Filed Dec. 22, 1969 2 Sheets-Sheet1 INVENTOR Mm, WW

ATTORNEY Feb 1971 H. RjlEscHEL 3563,04

CONTROL SYSTEMS FOR MINING EQUIPMENT Filed Dec. 22, 19 69 2 Sheets-Sheet2 FIG.2

INVENTOR 9 MwnQm ATTORNEY United States Patent 3,563,094 CONTROL SYSTEMSFOR MINING EQUIPMENT Hans Rieschel, Miltenberg, Germany, assignor toBergwerksverband G.m.b.H., Essen, Germany, a corporation of GermanyContinuation-impart of application Ser. No. 716,593, Mar. 27, 1968. Thisapplication Dec. 22, 1969, Ser. No. 887,037 Claims priority, applicationGermany, June 1, 1967, B 92,813 Int. Cl. G01l 7/00 U.S. Cl. 73-388 1Claim ABSTRACT OF THE DISCLOSURE The specification describes ahydraulic-pneumatic analog transducer for providing a pneumatic pressureindication of the hydraulic pressure existing in a hydraulic ram. Thetransducer makes use of a membrane of which one side is subjected to thehydraulic pressure while the other side, in accordance with thehydraulic pressure obtaining, varies in its distance from the end of atube. Air is caused to pass between the resulting annular gap betweenthe end of the tube and the membrane and the resulting pressure gradientis measured by means of a pneumatic pressure gauge.

CROSS REFERENCE TO RELATED APPLICATION This application constitutes acontinuation-in-part of application, Ser. No. 716,593, filed Mar. 27,1968, of Hans Rieschel and entitled Control Systems for Mining Equipmentnow abandoned.

BACKGROUND OF THE INVENTION The present invention relates moreparticularly to indicating apparatus for providing informationconcerning the pressure obtaining in hydraulic mine equipment at adistance from the equipment.

According to one previous proposal, see German specification 1,237,041,an electrical signal was to be provided varying in accordance with theworking pressure of hydraulic equipment, making use of a spring-loadeddouble piston which short-circuited a number of electrical contacts inaccordance with the displacement by the pressure. A disadvantage of thisdevice was, however, the limited number of signals that it could provideowing to the limitation on the number of contact pairs which could beused. A further disadvantage of the device was that extensiveprecautions and restrictions are necessary in connection with electricalequipment in mining.

SUMMARY OF THE INVENTION One particular object of the present inventionis to provide an apparatus for giving an indication of the hydraulicpressure existing in mine roof support units.

The present invention consists in an indicating apparatus for providinga pneumatic signal corresponding to the hydraulic pressure of a mineroof support ram, characterized in that the apparatus comprises: a bodydefining a chamber; a membrane extending across the chamber; duct meansfor applying hydraulic pressure to a first side of the membrane; a loopshaped wall having a rim adjacent to and substantially parallel to asecond side of the membrane, duct means for causing gas to flow betweenthe inside of the wall and the outside of it, this flow taking placebetween the wall and the membrane, and means responding to the pressuregradient existing between a space within the wall and around the wall.

In order to set the range of measurement of the apparatus, the lattercan comprise a tubular body which is fixed in Patented Feb. 16, 1971BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 of the drawings is adiagrammatic section of an apparatus in accordance with the invention;and

FIG. 2 is a section on the line A-B of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The apparatus comprises a body 1made up of two parts 2 and 3. The part 3 is in the form of ascrew-threaded ring screwed into the part 2 so as to press a circulardiaphragm or membrane 5 against a circular support shoulder face 4. Thepart 3 has a surface 6 opposite the face 4 and an annular seal 7 whichpresses the membrane 5 in a fluid-tight manner against the shoulder face4.

The screwed-in part 3 has a central hole 8 for supply ing oil of ahydraulic system to the membrane 5. The oil comes into contact with thefree face of the membrane 5, denoted by reference numeral 5a. The part 3also has sockets 10 and 11 of minor importance and it can be mounted inthe head plate H of a pit prop P. The hole 8 forms the connection withthe hydraulic pressure system of the pit prop P.

The part 2 has a circular hole 12 which forms part of a chamber on oneside of the membrane. Compressed air is passed through a union socket orduct 15 with a female thread 14 and passes through an annular channel 16under constant pressure into the chamber space 12. The socket 15 forms aconnection for the supply of compressed air.

On the opposite side of the body there is an outlet socket 19 providedwith a female thread 18, this socket serving for an output analoguesignal in accordance with the hydraulic pressure above the membrane 5.

In the centre of the annular chamber space 12 there is a tube 20 whoseupper end adjacent to the lower membrane face 5b forms a wall whichcooperates with the membrane face in forming a variable gap. The tube 20is provided with screw threads and is screwed into a hole 21 in the part2 and sealed by a gasket 22. The lower end of the tube 20 is providedwith a lock-nut 23. The vertical open ended passage 24 through the tube20 leads to the outside atmosphere.

In operation the duct 15 is connected with a supply of compressed airunder constant pressure. This air flows into the chamber 12 over the rimat the end of the tube 20 and thence into the inside of the tube 24 fromwhich it emerges to the outside atmosphere. If hydraulic pressure isapplied to the face 5a of the membrane, any variation in pressure leadsto a bending or bulging of the membrane 5 so as to vary the width of thegap between the rim of the tube 20 and the surface 5b of the membrane 5.As a result a greater or lesser pressure gradient across the gap iscreated and an air pressure is produced in the chamber 12 which ispassed out through duct 19.

As is schematically shown in the drawing, the analogue air pressure ispassed via a conduit 30 to a pressure gauge 31 whose pointer 32 shows ona scale a value proportional to the hydraulic pressure in the pit prop.By suitable calibration of the scale, taking the cross-sectional area ofthe piston of the pit prop into account, the scale can be made to readdirectly in tons or other units of weight acting 3 on the pit prop. Thepressure gauge or indicator can be provided at a considerable distancefrom the pit prop P.

It has been found that the apparatus, particularly the body with itsmembrane can be made to miniature dimensions.

What I claim is:

1. A device for indicating by pneumatic signal the hydraulic pressure ofa mine roof support pit prop having a head plate comprising: a bodymounted in said head plate provided with a chamber, a membrane extendingacross said chamber for dividing same into separate sections, duct meansfor conveying hydraulic pressure fluid from the pit prop to one sectionof said chamber, an open ended tube extending into the other section ofsaid chamber and terminating adjacent said membrane, means for adjustingsaid tube toward and away from said membrane, the outer end of said tubebeing open to the outside, means -for conducting a stream of air underconstant pressure through said other section of said chamber to pass tothe inside of said tube and thence to the outside, whereby any variationin hydraulic pressure causing flexing of said membrane so as to vary thegap between the end of said tube and said membrane creates a varyingpressure gradient across such gap, and gauge means connected to saidbody and communicating with said other section to visually indicate suchpressure variations in terms of hydraulic pressure.

References Cited FOREIGN PATENTS 580,140 7/1959 Canada 73-388 DONALD O.WOODIEL, Primary Examiner U.S. Cl. X.R. 73395, 406

